The investigations to be performed include continued studies of serum group II pepsinogen levels in controls and in patients with peptic ulcer disease, studies of the antigenic relationships of the two groups of pepsinogens to their respective pepsins and denatured pepsins, continued studies of pepsinogen phenotypes in controls and patients with peptic ulcer and studies of group I and group II pepsin secretion in gastric juice. BIBLIOGRAPHIC REFERENCE: Samloff I.M., Liebman W.M., Panitch N.M.; Serum group I pepsinogens by radioimmunoassay in control subjects and patients with peptic ulcer. Gastroenterology 69:83-90, 1975.